Technical Field
The present disclosure relates to processing of a message in a PLC system and, more particularly, to a message processing unit of a PLC system for efficiently processing a message through multiple filtering operations.
Description of the Related Art
A programmable logic controller (PLC) is an electronic device used for factory automation and process automation. The PLC is a general-purpose control device that is used by being programmed by a user. A PLC system generally includes a master module for controlling the entire PLC system and slave modules which are configured to perform a predetermined task for devices to which the PLC system is applied and to receive data from the devices and are capable of communicating the master module.
The PLC is required to have modules equipped with various functions to serve various purposes. Among such modules, the importance of a communication module configured to transmit data to a central processing unit (CPU) of the PLC and receive data from the CPU module has been highlighted.
Conventionally, a slave module receives all messages transmitted from a master module and analyzes the received messages. Thereafter, the slave modules discard the received message if the received message is not destined therefor. The slave modules communicate with the master module in this way in conventional cases.